Environmental Enrichment for the Horse- The Need for Companionship

As highlighted in the previous article ‘Environmental enrichment for the horse - the need to forage’, environmental enrichment can be defined as the additions and/or alterations made to a domesticated animal’s environment with the goal of improving welfare1. There are two types of environmental enrichment; the natural approach and the behavioural approach. The horse is internally motivated to perform specific behaviours and this article will focus on the horse’s need for companionship and social interaction.

Social behaviour

Horses are social animals regardless of whether they are wild or in a domesticated environment and have adapted to live with others. Wild horses live in herds comprising of a number of mares, their offspring and at least one male horse. Herd life is vital as a survival strategy and it provides much needed companionship, security2 and social behaviour is needed to help minimise conflict and enhance herd stability3. The mares will often stay together regardless of whether the male horse leaves the herd and the horses will commonly form pair bonds which can last a lifetime. Allogrooming (see figure one- also known as mutual grooming is the act of one horse grooming another) is a common sight with pair bonded horses but is also seen in non pair bonded horses. Allogrooming has been suggested to be an important social behaviour as it builds social bonds and can even lower the horse’s heart rate4. Play is another behaviour which is commonly observed in herds, especially within juvenile horses and helps to develop their social skills, physical motor skills and group cohesion.

Figure one: allogrooming

It is commonly observed that once a colt or filly is 1-3 years of age they will leave the family herd to join another or even establish their own. In addition to this, colts and stallions may join a “bachelor band” which is a herd consisting of up to 16 males5. Social isolation is rarely seen in the wild, although old and infirm stallions have been seen to live alone on occasion6.

The horse’s innate need for companionship

Compared to their free range counterparts, the variety of behaviours observed in domesticated horses has been altered due to modern husbandry practices. Domesticated horses are housed in a variety of different systems which provide varyinglevels of social interaction and companionship which can range from full interaction to no interaction at all, which some horses find frustrating and stressful.

It has been recognised that both long term and short term social isolation can impact horse welfare in a negative way as it has been found that horses are highly motivated to seek social interaction7. Consequently confinement and social isolation, along with other management factors, may all contribute to the development of stereotypies including crib-biting (see figure two), wind sucking, box walking and weaving8 which are rarely observed in the wild9. However, it is important to mention here that the individual’s coping style will determine how they cope with stress. This means that a stressed horse will not always stereotype in order to help them cope with a suboptimal environment (this will be discussed in a future article)10. It is therefore vital that horse owners and yard managers keep the behavioural needs of the horse at the forefront of their minds remembering that the behaviour of the horse has remained relatively unaltered by the domestication process11. Although it can be difficult to mimic all of the natural social interactions a horse would usually encounter in the wild there are natural enrichment and limited options for behaviour enrichment that can be used to help satisfy the social needs of the domesticated horse.

Figure two: a horse crib-biting

Keeping horses in groups

There is a large amount of evidence to express the benefits of keeping horses in groups; whether turned out (see figure three) or inside for example groups kept in a barn system. It has been found that eye temperature was significantly lower (which indicates a lower stress level) in horses which were group housed compared to being housed without social contact, with limited social contact and when pair housed12. It has also been found that housing which allows visual contact between horses has been suggested to reduce the risk of stereotypical behaviour13 and when both visual and tactile contact is increased weaving and nodding behaviour is decreased compared to when stabled with no contact with other horses14. A study15 has also found that sudden social isolation causes stress in young horses which resulted in a high prevalence of stereotypical behaviour development. A more recent study16 has also found that suddenly stabling horses individually, which were previously group housed, caused an increase in their cortisol concentrations (hormone related to stress response).

Figure three: three horses grazing together

Keeping horses in groups has advantages compared to keeping them individually and this is especially true for juvenile horses. A study17 has found that juvenile horses are less aggressive and have more refined social skills if they are kept in group housing compared to individual housing where they are deprived of social contact.This is reflected in their older age where adult horses can have increased levels of aggression if they were deprived of social contact as juveniles as their social skills are less developed. It has also been found that young horses adapt more easily to their initial training and show less unwanted behaviour if they are group housed compared to when housed individually18. Riding school horses have also been shown to have lower reactivity levels when they are group housed19. Keeping horses within groups gives more opportunity for horses to play which not only helps to improve social skills but also motor skills which in turn helps develop the musculoskeletal system20 and enhance gastrointestinal health21.

It is evident that keeping horses within groups impacts positively by increasing social interaction, so why is group housing not more widely used? It could be suggested that owners are concerned about the group dynamics and the risk of injury, for example their horse being kicked by another. Domestic herds are often unstable at livery yards as herd members are regularly moved around, added or replaced. This can cause disruption to the dynamics and social structure of the herd which could consequently lead to an increased level of aggression22, 23 particularly if resources are limited. Nevertheless, a study24 found that most new injuries after mixing horses into a herd were minor and that gender and age did not affect injury level. A study25 looked into the behaviour of group housed horses during turnout and found that 80% of aggressive interactions were only threats without any physical contact. It is important to mention here that they also found a higher amount of aggressive encounters between horses when they were in the smallest space allowance. In addition, a recent study26 has found that turning a group of horses out into a larger area reduces stress during short turnout periods which could in turn potentially reduce the risk of injury.

Mirrors

Weaving is an abnormal, stereotypic behaviour in the horse and can be defined by the horse swinging its head and neck in conjunction with swaying the body from side to side with the front legs27. Horses with established weaving express the stereotypic behaviour significantly less when they had a mirror in their stable28and those horses that were established weavers reduced the frequency of weaving29. Interestingly, a study has concluded that weaving and head nodding decreased when a known weaving horse had an image of a horse’s head (with pricked ears) in its stable. However, whilst the image could potentially reduce weaving in the short term it doesn’t mean that weaving is always reduced when horses are given social stimuli (whether visual, physical or otherwise). They found that weaving increased when yard activity was high and when the horses were anticipating a specific event, for example forage provision. This may suggest that weaving could be in response to frustration of the anticipation of an event rather than boredom30.

Conclusion

The horse’s innate need for social interaction and companionship is evident and both long and short term social isolation can impact horse welfare in a negative way. It is vital that horse owners and yard managers keep the behavioural needs of the horse at the forefront of their minds remembering that the behaviour of the horse has remained relatively unaltered by the domestication process. This means that horses have a high motivation to express certain behaviours, such as socialising, whether wild or domesticated. If expression of the behaviour is restricted due to environmental factors, it can lead to stress and frustration and consequently the development of stereotypies. Unfortunately, some modern day horse husbandry systems do not accommodate for the horse’s basic need for social interaction and many horses lead a solitary life which is against their natural instincts. There are steps which owners and yard managers can take, either through environmental or behavioural enrichment, to increase social opportunities and help to improve welfare.

15)Visser, E.K., Ellis, A.D. and Van Reenen, C.G., 2008. The effect of two different housing conditions on the welfare of young horses stabled for the first time. Applied Animal Behaviour Science, 114(3), pp.521-533.

28)Mills, D.S. and Riezebos, M., (2005). The role of the image of a conspecific in the regulation of stereotypic head movements in the horse. Applied Animal Behaviour Science, 91(1), pp.155-165.

29)McAfee, L.M., Mills, D.S. and Cooper, J.J., (2002). The use of mirrors for the control of stereotypic weaving behaviour in the stabled horse. Applied Animal Behaviour Science, 78(2), pp.159-173

30)Mills, D.S. and Davenport, K., (2002). The effect of a neighbouring conspecific versus the use of a mirror for the control of stereotypic weaving behaviour in the stabled horse. Animal Science, 74(1), pp.95-101.